diff --git a/module_usb_audio/endpoint0/endpoint0.c b/module_usb_audio/endpoint0/endpoint0.c
index 89963257..8213e87f 100755
--- a/module_usb_audio/endpoint0/endpoint0.c
+++ b/module_usb_audio/endpoint0/endpoint0.c
@@ -76,10 +76,10 @@ unsigned char mixer1Crossbar[18];
 short mixer1Weights[18*8];
 
 unsigned char channelMap[NUM_USB_CHAN_OUT + NUM_USB_CHAN_IN + MAX_MIX_COUNT];
-#if NUM_USB_CHAN_OUT > 0
+#if (NUM_USB_CHAN_OUT > 0)
 unsigned char channelMapAud[NUM_USB_CHAN_OUT];
 #endif
-#if NUM_USB_CHAN_IN > 0
+#if (NUM_USB_CHAN_IN > 0)
 unsigned char channelMapUsb[NUM_USB_CHAN_IN];
 #endif
 unsigned char mixSel[MIX_INPUTS];
@@ -337,7 +337,7 @@ void Endpoint0(chanend c_ep0_out, chanend c_ep0_in, chanend c_audioControl,
                                 }
                             }
                         }
-#if defined(OUTPUT) && defined(INPUT)
+#if (NUM_USB_CHAN_OUT > 0) && (NUM_USB_CHAN_IN > 0)
                         /* Check for stream start stop on output and input audio interfaces */
                         if(sp.wValue && !g_interfaceAlt[1] && !g_interfaceAlt[2])
                         {
@@ -354,7 +354,7 @@ void Endpoint0(chanend c_ep0_out, chanend c_ep0_in, chanend c_audioControl,
                             /* if input stop and input running and output not running */
                             UserAudioStreamStop();
                         }
-#elif defined(OUTPUT) || defined(INPUT)
+#elif (NUM_USB_CHAN_OUT > 0) || (NUM_USB_CHAN_IN > 0)
                         if(sp.wValue && (!g_interfaceAlt[1]))
                         {
                             /* if start and not currently running */
diff --git a/module_usb_audio/usb_buffer/decouple.xc b/module_usb_audio/usb_buffer/decouple.xc
index 092396cd..4ecfd97e 100644
--- a/module_usb_audio/usb_buffer/decouple.xc
+++ b/module_usb_audio/usb_buffer/decouple.xc
@@ -648,7 +648,7 @@ void decouple(chanend c_mix_out,
     int aud_from_host_flag=0;
     xc_ptr released_buffer;
 #endif
-#if (NUM_USB_CHAN_OUT > 0)
+#if (NUM_USB_CHAN_IN > 0)
     int aud_to_host_flag = 0;
 #endif
 
@@ -721,7 +721,7 @@ void decouple(chanend c_mix_out,
     XUD_SetReady_OutPtr(aud_from_host_usb_ep, g_aud_from_host_wrptr+4);
 #endif
 
-#if (NUM_USB_CHAN_OUT > 0)
+#if (NUM_USB_CHAN_IN > 0)
     /* Wait for usb_buffer to set up */
     while(!aud_to_host_flag)
     {